mountroot: On failure return ENOENT, not ENODEV

[trasz]

Summary

As it is now, if we wait for a device node to appear
and it never happens, we return ENODEV ("failed with error 19").
Use ENOENT instead; ENODEV might be quite misleading.

Sponsored By: EPSRC

[kib]

I do not object, mostly because I cannot make an opinion. You mentioned that 'ENODEV might be quite misleading'. Can you provide more info, and explain what this change gives us?

[trasz]

My first thought about ENODEV was something about GEOM. ENOENT, on the other hand, would make it obvious what's going on: the root device node is simply not there.

[kib]

As I said, I do not see a point, but I do not object.